German Utility Model No. 1 840 499 discloses a switch built into the handle of a resectoscope for opening and closing the high-frequency circuit. The switch is operated with the thumb of the hand grasping the handle.
A disadvantage of such built-in switches is that their mechanisms can be impaired by the temperatures occurring during sterilisation of an instrument, and such mechanisms may be damaged by the ingress of water thereinto. Also, with such instruments with which a coagulator is used the electrical potential of the coagulator is applied to the input wires of the handle and to the switch contacts so long as the coagulator is switched on. Comprehensive means must, therefore, be provided for electrically insulating the switch and the switch housing, that is to say, basically the handle, in order to safeguard the patient and the operator.